Flame-retardant epoxy resin composition, prepregs containing the same, laminated sheets and printed wiring boards

ABSTRACT

A flame retardant epoxy resin composition comprises a phosphorus atom-containing flame retardant polyester resin in addition to essential components of an epoxy resin and a curing agent. The phosphorus atom-containing flame retardant polyester resin is obtained by a condensation reaction or a polycondensation reaction of a reactive phosphorus-containing compound represented by the structural formula (I). By use of the phosphorus atom-containing flame retardant polyester resin as a halogen-free flame retardant, it is possible to achieve flame retardancy, reduce an amount of poisonous gas emitted when ignited, and improve moldability. In addition, a cured product of this epoxy resin composition is excellent in heat resistance, water resistance, chemical resistance, solder resistance, moisture resistance and tracking resistance as well as the flame retardancy.

TECHNICAL FIELD

The present invention relates to a flame retardant epoxy resincomposition having high flame resistance, which emits a little amount ofpoisonous gas when ignited, and prepregs, laminates and printed wiringboards, which are produced by use of the same epoxy resin composition.

BACKGROUND ART

Epoxy resin having excellent performance such as heat resistance,adhesion and electric properties (electric insulation) has been widelyused as a material for various electric and electronic parts.

In the application of electric laminates typified by glass epoxylaminates for printed wiring boards, high flame retardancy (“V-0” inUL-94 flammability test) is desired. For this purpose, a halogencontaining compound such as a brominated epoxy resin is usually used.For example, it is disclosed in Japanese Patent Early Publications[kokai] No. 5-9394, No. 9-125037, and No. 9-283876 that a resincomposition comprising an epoxy resin containing the brominated epoxyresin as the main component and an epoxy resin curing agent such asdicyandiamide and phenol compounds are used to manufacture an epoxyresin laminate for printed circuit board.

However, the use of such a halogen containing compound is recentlyfocused as a cause of the environmental destruction typified by dioxin.In addition, dissociation of halogen under high temperature conditionhas a bad influence on long-term electric reliability. Therefore, it isstrongly desired to reduce the amount used of the halogen containingcompound, or develop a flame retardant using an alternative compound forthe halogen containing compound or a new method of imparting flameretardancy to the resin composition.

As a substitute technique for the flame retardancy imparting methodusing the halogen containing compound, Japanese Patent Early Publication[kokai] No. 10-193516 discloses to use a phosphoric ester compound asthe flame retardant.

However, when the phosphoric ester compound is used as the flameretardant, a large amount of the flame retardant is needed to achievehigh frame retardancy (for example, “V-0” in UL-94 flammability test).This leads to deterioration in properties of the resultant moldedarticle such as heat resistance, water resistance, and chemicalresistance to acid and alkali.

SUMMARY OF THE INVENTION

Therefore, a primary concern of the present invention is to provide aflame retardant epoxy resin composition, which has the capability ofreducing an amount of poisonous gas emitted when ignited, and impartingexcellent flame retardancy, heat resistance, water resistance, chemicalresistance as well as solder resistance, moisture resistance andtracking resistance to a molded article thereof.

That is, the flame retardant epoxy resin composition of the presentinvention comprises an epoxy resin (A), curing agent (B) and aphosphorus atom-containing flame retardant polyester resin (C), andcharacterized in that the phosphorus atom-containing flame retardantpolyester resin (C) is obtained by a condensation reaction or apolycondensation reaction of a reactive phosphorus-containing compound(s) represented by the following structural formula (I).

According to the present invention, since this flame retardant epoxyresin composition contains the phosphorus atom-containing flameretardant polyester resin (C), which does not contain halogen as theflame retardant, it is possible to impart high flame retardancy to theresin composition, reduce the amount of poisonous gas generated whenignited as a result of a reduction in halogen content in the resincomposition, and provide good moldability. In addition, as describedabove, there are advantages that a cured product of the epoxy resincomposition is excellent in heat resistance, water resistance, chemicalresistance as well as flame retardancy, solder resistance, moistureresistance and tracking resistance.

It is preferred that a part or all of the curing agent (B) contains anovolac resin. In addition, it is preferred that an epoxy equivalent ofthe epoxy resin (A) is in a range of 100 to 10000 g/eq. In these cases,the crosslinking density of the cured product of the flame retardantepoxy resin composition increases, so that glass transition point “Tg”,heat resistance and solder resistance are improved and particularly,performance needed in the laminate application is improved.

Moreover, it is preferred that the epoxy resin (A) consists of an epoxyresin having no halogen atom in its molecular structure. In this case,since the halogen content in the resin composition is further reduced,it is possible to more effectively prevent the generation of poisonousgas when ignited.

Another concern of the present invention is to provide a prepregobtained by impregnating the flame retardant epoxy resin compositiondescribed above into a substrate, laminate obtained by molding theprepreg, and a printed wiring board obtained by forming a conductivewiring on a surface or both surfaces of the thus obtained laminate.These exhibit excellent flame retardancy by use of the halogen-freeflame retardant. That is, since the prepreg, laminate and the printedwiring board are produced by use of the phosphorus atom-containing flameretardant polyester resin (C) as the flame retardant not containinghalogen, it is possible to impart high flame retardancy to them, andreduce the amount of poisonous gas generated when ignited as a result ofa reduction in halogen content in the resin composition. In addition, amolded article obtained by molding the prepreg, the laminate and theprinted wiring board exhibit various excellent properties such as heatresistance, water resistance, chemical resistance, flame retardancy,solder resistance, moisture resistance and tracking resistance. It ispreferred to form a metal foil on at least one surface of the laminateby laminate molding.

These and additional features of the present invention and advantagesbrought thereby will be understood from the base mode for carrying outthe invention described below.

BEST MODE FOR CARRYING OUT THE INVENTION

A flame retardant epoxy resin composition of the present invention,prepregs, laminates and printed wiring boards, which contain the samecomposition, are explained in detail according to preferred embodiments.

As described above, the flame retardant epoxy resin composition of thepresent invention is characterized by containing a phosphorusatom-containing flame retardant polyester resin (C) in an epoxy resincomposition having an epoxy resin (A) and a curing agent (B) asessential components. In addition, to prepare the epoxy resincomposition of the present invention, a halogen containing material canbe used. However, it is preferred to prepare the flame retardant epoxyresin composition without using the halogen containing material. Whenpreparing the halogen-free flame retardant epoxy resin composition, itis permitted that a small amount of the halogen containing material isinevitably mixed in the production process.

As the epoxy resin (A) used in the present invention, which is notspecifically limited, it is preferred to use only a halogen-freecompound. Such an epoxy resin (A) comprises, for example, a bisphenoltype epoxy resin such as bisphenol A-type epoxy resin, bisphenol F-typeepoxy resin, 2,2′,6,6′-tetramethyl bisphenol A-type epoxy resin,bisphenol S-type epoxy resin, bisphenol AD-type epoxy resin, tetramethylbisphenol A-type epoxy resin, and bis-β-trifluoromethyl diglycidylbisphenol A-type epoxy resin; naphthalene type epoxy resin such as1,6-diglycidyloxynaphthalene type epoxy resin,1-(2,7-diglycidyloxynaphthyl)-1-(2-glycidyloxynaphthyl)methane,1,1-bis(2,7-diglycidyloxynaphthyl)methane, and1,1-bis(2,7-diglycidyloxynaphthyl)-1-phenyl-methane; other 2-functionalepoxy resin such as bisphenol type epoxy resin, bisphenolhexafluoroacetone diglycidylether and resorcinol glycidylether; novolactype epoxy resin such as phenol novolac type epoxy resin, orthocresolnovolac type epoxy resin, bisphenol A novolac type epoxy resin, andbisphenol AD novolac type epoxy resin; epoxy resin obtained bycopolymerization between bisphenol type epoxy resin and novolac typeepoxy resin through bisphenol; cyclic aliphatic epoxy resin typified byan epoxy compound of a polyaddition product of dicyclopentadiene andphenol; glycidyl ester type epoxy resin such as phthalic acid diglycidylester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic aciddiglycidyl ester, diglycidyl p-oxybenzoic acid ester, dimmer acidglycidyl ester, and triglycidyl ester; glycidylamine type epoxy resinsuch as tetraglycidyl aminodiphenylmethane, triglycidyl p-aminophenol,and tetraglycidyl m-xylylenediamine; heterocyclic epoxy resin such ashydantoin type epoxy resin and triglycidyl isocyanate; other epoxyresins such as phloroglucinol triglycidyl ether, trihydroxybiphenyltriglycidyl ether, trihydroxyphenylmethane triglycidyl ether, glycerintriglycidyl ether, 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-(2,3-epoxypropoxy)phenyl]ethyl]phenyl]propane, 1,3-bis[4-[1-[4-[(2,3 epoxypropoxy)phenyl]-1-[4-[1-[4-(2,3-epoxypropoxy)phenyl]-1-methylethyl]phenyl]ethyl]phenoxy]-2-propanol,tetrahydroxy phenylethane tetraglycidyl ether, tetraglycidylbenzophenone, bisresorcinol tetraglycidyl ether, and tetraglycidoxybiphenyl. Each of the epoxy resins listed above may be used by itself,or a combination of two or more thereof may be used. In addition, anepoxy resin obtained by denaturing the epoxy resin listed above may beused simultaneously.

In these epoxy resins, it is preferred that the epoxy equivalent is in arange of 100 to 10000 g/eq. That is, when the epoxy equivalent is notlarger than 10000 g/eq, the crosslinking density of a cured productincreases, and the glass transition temperature “Tg”, heat resistanceand the solder resistance are improved. In addition, an improvement inperformance of the laminate is achieved.

In addition, it is preferred to use a novolac type epoxy resin as a partor all of the epoxy resin because a molded article having the high “Tg”,high water resistance and the solder resistance is obtained. In the caseof using the novolac type epoxy resin, it is particularly preferred thata content of the novolac type epoxy resin is 20 wt % or more withrespect to the total amount of the epoxy resin (A). When the content issmaller than 20 wt %, it may be difficult to sufficiently impart thehigh Tg, high water resistance and the solder resistance to the moldedarticle.

In the present invention, an epoxy reactive diluent such as cyclohexeneoxide, tricyclodecene oxide and cyclopentene oxide may be used togetherwith the epoxy resin (A).

As the curing agent (B), a curing agent generally used for epoxy resinsis available. For example, it is possible to use a novolac resin; latentamine curing agent such as dicyandiamide, imidazole, BF₃-amine complex,and guanidine derivative; aromatic amine such as metaphenylenediamine,diaminodiphenylmethane, and diaminodiphenylsulfone; nitrogen atomcontaining curing agent such as cyclophosphazene oligomer; polyamideresin; acid anhydride curing agent such as maleic anhydride, phthalicanhydride, hexahydrophthalic anhydride and pyromellitic acid anhydride.Each of these curing agents (B) may be used by itself, or a combinationof two or more thereof may be used.

In addition, it is preferred to use a novolac resin as a part or all ofthe curing agent (B). Such a novolac resin is not specifically limited.For example, it is possible to use the novolac resin, in which a phenolsuch as phenol, cresol, xylenol, ethylphenol, n-propylphenol,isopropylphenol, n-butylphenol, isobutylphenol, tertiary butylphenol,secondary butylphenol, n-hexylphenol, n-octylphenol, n-nonylphenol,n-dodecylphenol, isoamylphenol, isooctylphenol, tertiary aminophenol,tertiary octylphenol, and bisphenol A is crosslinked by formalin. Fromthe viewpoint of excellent heat resistance, it is preferred to use aphenol novolac resin, in which phenol is crosslinked by formalin, or acresol novolac resin, in which cresol is crosslinked by formalin.

In addition, it is preferred that a softening point of the novolac resinis in a range of 50 to 150° C. to achieve good balance between heatresistance and easiness of impregnation into a cloth-like substrate forelectric laminate.

An additive amount of the curing agent (B) in the composition isdetermined in consideration of the kinds of components of the resincomposition, moldability of prepregs, and the moldability of theprepregs at the time of curing and molding, and therefore not limitedspecifically. For example, when using the novolac resin as the curingagent (B), it is preferred that a hydroxyl equivalent of the novolacresin is in a range of 0.8 to 1.2 with respect to the epoxy resin (A).When the hydroxyl equivalent is out of this range, insufficient curingmay happen.

If necessary, the epoxy resin composition of the present invention cancontain a hardening accelerator. A conventional hardening accelerator isavailable. For example, it is possible to use a tertiary amine such asbenzyldimethylamine, imidazole, organic acid metallic salt, Lewis acid,or an amine complex salt. Each of these compounds may be used by itself,or a combination of two or more thereof may be used. An additive amountof the hardening accelerator in the composition is determined inconsideration of the kinds of components of the resin composition,moldability of prepregs, and the moldability of the prepregs at the timeof curing and molding, and therefore not limited specifically. Forexample, it is preferred that the additive amount of the hardeningaccelerator is in a range of 0.001 to 10 wt % with respect to the totalamount of the epoxy resin (A).

The phosphorus atom-containing flame retardant polyester resin (C) canbe obtained by a condensation reaction or a polycondensation reaction ofa reactive phosphorus-containing compound (s).

As the reactive phosphorus-containing compound (s), a compoundrepresented by the following general formula (I) is preferably used fromthe viewpoints of easiness of reaction and excellent flame retardancy.

As described above, the phosphorus atom-containing flame retardantpolyester resin (C) can be obtained by the condensation reaction or thepolycondensation reaction of the reactive phosphorus-containing compound(s). Concretely speaking, the phosphorus atom-containing flame retardantpolyester resin (C) can be obtained by adding the reactivephosphorus-containing compound (s) into a reaction vessel, graduallyelevating the temperature, and then keeping it at a temperature range of160 to 280° C. under a reduced pressure, for example, lower than 6.7 hPa(5 mmHg). In this reaction system, a conventional catalyst such astitanium, antimony, lead, zinc, magnesium, calcium, manganese, andalkali metal compounds may be added at an arbitrary timing.

It is preferred that the number average molecular weight of thephosphorus atom-containing flame retardant polyester resin (C) used inthe epoxy resin composition of the present invention is in a range of500 to 50000. When the number average molecular weight is in the aboverange, it is possible to provide the phosphorus atom-containing flameretardant polyester resin (C) having excellent flame retardancy, andimpart remarkably improved flame retardancy and heat resistance to acured product of the epoxy resin composition prepared by use of thisphosphorus atom-containing flame retardant polyester resin (C).

A content of the phosphorus atom-containing flame retardant polyesterresin (C) in the epoxy resin composition is not specifically limited. Toobtain the epoxy resin composition having excellent tracking resistance,moisture resistance, solder resistance, heat resistance and flameretardancy of a cured product thereof, it is preferred to add thephosphorus atom-containing flame retardant polyester resin (C) such thata content of phosphorus atoms in the total amount of the composition(the phosphorus content based on phosphorus conversion) is 0.02% or moreby weight ratio. In this case, an upper limit of the content is notlimited specifically. For example, it is preferred that the content ofphosphorus atoms in the total amount of the composition is 9% or less byweight ratio.

The epoxy resin composition of the present invention can contain apolyester resin other than the phosphorus atom-containing flameretardant polyester resin (C). In the case of adding the other polyesterresin, it is preferred that the content of the phosphorusatom-containing flame retardant polyester resin (C) is 10 wt % or morewith respect to the total amount of these polyester resins.

In addition, the epoxy resin composition of the present invention cancontain an organic solvent (D) in addition to the components describedabove, if necessary. In particular, when preparing a varnish forelectric laminates, it is preferred to use the components (A), (B), (C)and (D) as the essential components. Of course, even when the epoxyresin composition of the present invention is used for anotherapplications such as a coating material, the component (D) may be usedtogether with the components (A) to (C).

The organic solvent (D) is not specifically limited. For example, it ispossible to use acetone, methylethylketone, toluene, xylene,methylisobutylketone, ethyl acetate, ethyleneglycol monomethylether,N,N-dimethylformaldehyde, methanol, ethanol, isopropylalcohol,n-butanol, methoxy propanol, ethyl carbitol, toluene or cyclohexanone.Each of these solvents may be used by itself, or a combination of two ormore thereof may be used.

An amount used of the organic solvent (D) is not specifically limited.From the viewpoints of easiness of impregnation of the epoxy resincomposition into a substrate in the case of preparing the prepreg andgood adhesion between the resin composition and the substrate, it ispreferred to add the organic solvent (D) such that a solid concentrationin the varnish is 30 wt % or more, and particularly in a range of 40 to70 wt %.

Furthermore, the epoxy resin composition of the present invention cancontain various additives, flame retardant and a filler, if necessary.In particular, it is preferred to add an inorganic filler (E) to obtainfurther improved flame retardancy.

The inorganic filler (E) is not specifically limited. For example, it ispossible to use silica, talc, calcium carbonate, magnesium carbonate,aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesiumoxide, aluminum silicate, lithium aluminum silicate, barium titanate,barium sulfate, silicon nitride or boron nitride.

In addition, it is preferred to add the inorganic filler (E) such that acontent of the inorganic filler (E) in the composition is 150 parts byweight or less with respect to 100 parts by weight of the total of theepoxy resin (A), curing agent (B) and the flame retardant (C). Even whenusing a larger amount of the inorganic filler (E) than 150 parts byweight, the flame retardancy is almost the same as above. On thecontrary, deterioration in performance of the laminate such as drillingworkability may happen.

Moreover, various kinds of additives such as penetrating agent andleveling agent may be added. However, to obtain remarkable effects ofthe present invention, it is recommended that the epoxy resincomposition does not contain those additives. In the case of using thoseadditives, it is preferred that the content in the resin composition is5 wt % or less.

As described above, the epoxy resin composition of the present inventionis particularly effective in the application of electric laminates. Amethod of manufacturing a laminate by use of the epoxy resin compositionis not specifically limited. In the case of not using the organicsolvent (D), for example, a solid composition prepared by the componentsof the epoxy resin composition is melted by heating, and the meltedcomposition is impregnated into a substrate with a required resincontent (preferably 30 to 70 wt %). On the other hand, when using theorganic solvent (D), a varnish is prepared by compounding the componentsof the epoxy resin composition, and impregnated into the substrate withthe required resin content (preferably 30 to 70 wt %) to obtain theprepreg. The laminate can be produced by hot pressing a required number(preferably 1 to 10) of the prepregs.

To obtain a metal clad laminate, for example, a metal foil(s) such ascopper foil is placed on a surface or both surfaces of a required number(preferably, 1 to 10) of prepregs, and then the resultant assembly ishot pressed.

In addition, conductive wirings can be formed on a surface or bothsurfaces of the laminate or the metal clad laminate described above by asubtractive process or an additive process to obtain a printed wiringboard.

The substrate used to prepare the prepreg is not specifically limited.For example, as the substrate available to prepare the prepreg, it ispossible to use an inorganic fiber woven or nonwoven fabric such as aglass woven or nonwoven fabric or an organic fiber woven or nonwovenfabric such as an aramid resin woven or nonwoven fabric.

As pressure and temperature conditions at the time of forming thelaminate, for example, it is preferred that the temperature is in arange of 120 to 220° C., the pressure is in a range of 2 to 10 MPa, andthe keep time is in a range of 10 to 240 minutes.

As described above, the epoxy resin composition of the present inventionis very effective in the application for manufacturing the electriclaminates. However, it is available in various applications such asadhesives, cast molding, and coatings by appropriately combining withthe curing agent. For example, the resin composition can be applied asan adhesive on a copper foil, and then dried to obtain a semi-curedproduct, which is applicable in a buildup process.

Thus, according to the epoxy resin composition of the present invention,an anti-halogen, flame retardant cured product can be obtained withoutdeteriorating the heat resistance. Therefore, it is suitable for variousapplications such as sealing, laminating and coating, and particularlyfor glass epoxy laminates or an IC sealing material. In addition, due toexcellent adhesion with metals, it is possible to provide the epoxyresin composition for coating, which is suitable as resist and coatingmaterials.

EXAMPLES

Next, the present invention is explained according to Examples, which donot limit the invention. Unless otherwise specified, “parts” used in thefollowing Synthesis Examples, Examples and Comparative Examples is basedon weight. In addition, the number average molecular weight of polyesterresins of the Synthesis Examples 1 to 3, physical properties in Examples1 to 6 and Comparative Examples 1 to 3 were measured by the followingmethods.

(1) Measurement of Number Average Molecular Weight

With respect to each of samples, a THF solution was prepared such thatthe solid content is 10 mg/ml, and the number average molecular weightwas measured at an injection amount of 100 micro-liters under thefollowing measuring conditions.

-   GPC measuring device: “SHODEX-SYSTEM 11” manufactured by SHOWA DENKO    K.K.-   Column: 4-series moving beds of SHODEX “KF-800P”, “KF-805”, “KF-803”    and “KF-801” (all manufactured by SHOWA DENKO K.K.)-   THF Flow Amount: 1 ml/min-   Column Temperature: 45° C.-   Detector: RI-   Conversion: polystyrene    (2) Flame Retardancy

It was evaluated according to UL-94 flammability test method.

(3) Tracking Resistance

With respect to each of the samples, according to UL-1410, electrodesare disposed on a substrate, and a voltage corresponding to 50 drops wasdetermined from an obtained titration number-voltage curve.

(4) Peel Strength

It was evaluated according to JIS C 6481.

(5) Heat Resistance

With respect to each of the samples, copper clad laminates having thesize of 25 mm×25 mm were prepared as test pieces, and floated in asolder bath at 280° C. for different times of 5, 10, 15 and 20 minutes.Then, the occurrence of blister was checked according to the followingcriteria:

-   {circle around (o)}: No blister occurred.-   ∘: Blister partially occurred.-   Δ: Blister largely occurred.-   ×: Blister occurred in the entire surface of the test piece.    (6) Moisture Resistance

With respect to each of samples, after a pressurized steam treatment wasperformed under 2 atm at 120° C., it was immersed in a solder bath at280° C. for 10 seconds. Then, the occurrence of blister was checkedaccording to the following criteria.

-   {circle around (o)}: No blister occurred.-   ∘: Blister partially occurred.-   Δ: Blister largely occurred.-   ×Blister occurred in the entire surface of the test piece.    <Synthesis of Phosphorus Atom-Containing Flame Retardant Polyester    Resin (C)>

Synthesis Example 1

600.0 parts of a reactive phosphorus-containing compound (s) (thereactive phosphorus-containing compound (s) represented by the abovechemical formula (I), manufactured by SANKO CO., LTD, product name“M-ester”, 63% ethylene glycol solution) and 0.1 parts of potassiumtitanium oxalate were added into a reaction vessel, and then heated,while being agitated. Next, the reaction vessel was graduallydepressurized at 250° C., and a copolymerization reaction proceeded for50 minutes under conditions of 250° C. and 0.5 mmHg (66.7 Pa) to obtaina phosphorus atom-containing flame retardant polyester resin (C-1.)having the number average molecular weight of 5100.

Synthesis Example 2

In the synthesis Example 1, the copolymerization reaction proceeded for10 minutes to obtain a phosphorus atom-containing flame retardantpolyester resin (C-2) having the number average molecular weight of 520.

Synthesis Example 3

In the synthesis Example 1, the copolymerization reaction proceeded for180 minutes to obtain a phosphorus atom-containing flame retardantpolyester resin (C-3) having the number average molecular weight of11000.

Example 1

100 parts of a phenol novolac type epoxy resin “EPICLON N-770”(manufactured by DAINIPPON INK AND CHEMICALS, INCORPORATED, epoxyequivalent 189 g/eq), 70 parts of a bisphenol A-type epoxy resin“EPICLON 1051” (manufactured by DAINIPPON INK AND CHEMICALS,INCORPORATED, epoxy equivalent 470 g/eq), 72 parts of a novolac typephenol resin “PSM-4261” (manufactured by Gunei Chemical Industry Co.,Ltd., hydroxyl equivalent 106 g/eq, softening point 80° C.) as a curingagent, 85 parts of the phosphorus atom-containing flame retardantpolyester resin (C-1) obtained in the Synthetic Example 1, and 0.3 partsof 2-ethyl-4-methyl imidazole as a hardening accelerator were solved ina mixed solvent of 80 parts of methyl cellosolve and 90 parts of methylethyl ketone to prepare an epoxy resin composition (epoxy resinvarnish).

The resin varnish was impregnated in a glass cloth (manufactured byAsahi-Schwebel Co., Ltd., Type-7628, Thickness: 0.18 mm), and then driedin B stage by a 170° C. drying machine, so that the gel time of theresultant prepreg measured at 170° C. is approximately 120 seconds. Thethus obtained epoxy resin prepreg has a resin content of 45 wt %.

8 sheets of the obtained prepregs were stacked, and copper foils havinga thickness of 18 μm were placed on both surfaces of the stacking. Theresultant assembly was cured at the temperature of 170° C. under thepressure of 3.9 MPa (40 kg/cm²) for the heating time of 90 minutes toobtain a laminate having a thickness of about 1.6 mm.

With respect to the obtained laminate, the heat resistance (solderresistance), moisture resistance, peel strength were measured under theabove-described measurement conditions. In addition, after the copperfoils were removed from the laminate by dissolving, the trackingresistance and the flame retardancy were evaluated under the abovemeasurement conditions. Results are shown in Table 1.

Example 2

An epoxy resin composition was prepared according to the same method asExample 1 except for using the phosphorus atom-containing flameretardant polyester resin (C-2) obtained in the Synthetic Example 2 inplace of the phosphorus atom-containing flame retardant polyester resin(C-1) obtained in the Synthetic Example 1. By use of the epoxy resincomposition, epoxy resin prepregs and a laminate were produced andevaluated, as in the case of Example 1. Results are shown in Table 1.

Example 3

An epoxy resin composition was prepared according to the same method asExample 1 except for using the phosphorus atom-containing flameretardant polyester resin (C-3) obtained in the Synthetic Example 3 inplace of the phosphorus atom-containing flame retardant polyester resin(C-1) obtained in the Synthetic Example 1. By use of the epoxy resincomposition, epoxy resin prepregs and a laminate were produced andevaluated, as in the case of Example 1. Results are shown in Table 1.

Example 4

110 parts of a cresol novolac type epoxy resin “EPICLON N-665”(manufactured by DAINIPPON INK AND CHEMICALS, INCORPORATED, epoxyequivalent 206 g/eq), 70 parts of a bisphenol A-type epoxy resin“EPICLON 1051” (manufactured by DAINIPPON INK AND CHEMICALS,INCORPORATED, epoxy equivalent 470 g/eq), 72 parts of a novolac typephenol resin “PSM-4261” (manufactured by Gunei Chemical Industry Co.,Ltd., hydroxyl equivalent 106 g/eq, softening point 80° C.) as a curingagent, 85 parts of the phosphorus atom-containing flame retardantpolyester resin (C-1) obtained in the Synthetic Example 1, and 0.3 partsof 2-ethyl-4-methyl imidazole as a hardening accelerator were solved ina mixed solvent of 80 parts of methyl cellosolve and 90 parts of methylethyl ketone to prepare an epoxy resin composition (epoxy resinvarnish).

By use of the epoxy resin composition, epoxy resin prepregs and alaminate were produced and evaluated, as in the case of Example 1.Results are shown in Table 1.

Example 5

An epoxy resin composition was prepared according to the same method asExample 4 except for using the phosphorus atom-containing flameretardant polyester resin (C-2) obtained in the Synthetic Example 2 inplace of the phosphorus atom-containing flame retardant polyester resin(C-1) obtained in the Synthetic Example 1. By use of the epoxy resincomposition, epoxy resin prepregs and a laminate were produced andevaluated, as in the case of Example 1. Results are shown in Table 1.

Example 6

An epoxy resin composition was prepared according to the same method asExample 4 except for using the phosphorus atom-containing flameretardant polyester resin (C-3) obtained in the Synthetic Example 3 inplace of the phosphorus atom-containing flame retardant polyester resin(C-1) obtained in the Synthetic Example 1. By use of the epoxy resincomposition, epoxy resin prepregs and a laminate were produced andevaluated, as in the case of Example 1. Results are shown in Table 1.

Comparative Example 1

100 parts of a phenol novolac type epoxy resin “EPICLON N-770”(manufactured by DAINIPPON INK AND CHEMICALS, INCORPORATED, epoxyequivalent 189 g/eq), 70 parts of a bisphenol A-type epoxy resin“EPICLON 1051” (manufactured by DAINIPPON INK AND CHEMICALS,INCORPORATED, epoxy equivalent 470 g/eq), 72 parts of a novolac typephenol resin “PSM-4261” (manufactured by Gunei Chemical Industry Co.,Ltd., hydroxyl equivalent 106 g/eq, softening point 80° C.), and 0.3parts of 2-ethyl-4-methyl imidazole as a hardening accelerator weresolved in a mixed solvent of 60 parts of methyl cellosolve and 70 partsof methyl ethyl ketone to prepare an epoxy resin composition (epoxyresin varnish). By use of the resin varnish, epoxy resin prepregs and alaminate were produced and evaluated, as in the case of Example 1.Results are shown in Table 1.

Comparative Example 2

100 parts of a phenol novolac type epoxy resin “EPICLON N-770”(manufactured by DAINIPPON INK AND CHEMICALS, INCORPORATED, epoxyequivalent 189 g/eq), 70 parts of a bisphenol A-type epoxy resin“EPICLON 1051” (manufactured by DAINIPPON INK AND CHEMICALS,INCORPORATED, epoxy equivalent 470 g/eq), 72 parts of a novolac typephenol resin “PSM-4261” (manufactured by Gunei Chemical Industry Co.,Ltd., hydroxyl equivalent 106 g/eq, softening point 80° C.), 0.3 partsof 2-ethyl-4-methyl imidazole as a hardening accelerator, and 80. partsof a phosphate ester flame retardant “PX-200” (manufactured by DAIHACHICHEMICAL INDUSTRY CO., LTD.) were solved in a mixed solvent of 80 partsof methyl cello solve and 90 parts of methyl ethyl ketone to prepare anepoxy resin composition (epoxy resin varnish). By use of the resinvarnish, epoxy resin prepregs and a laminate were produced andevaluated, as in the case of Example 1. Results are shown in Table 1.

Comparative Example 3

100 parts of a phenol novolac type epoxy resin “EPICLON N-770”(manufactured by DAINIPPON INK AND CHEMICALS, INCORPORATED, epoxyequivalent 189 g/eq), 70 parts of a bisphenol A-type epoxy resin“EPICLON 1051” (manufactured by DAINIPPON INK AND CHEMICALS,INCORPORATED, epoxy equivalent 470 g/eq), 72 parts of a novolac typephenol resin “PSM-4261” (manufactured by Gunei Chemical Industry Co.,Ltd., hydroxyl equivalent 106 g/eq, softening point 80° C.), and 0.3parts of 2-ethyl-4-methyl imidazole as a hardening accelerator weresolved in a mixed solvent of 80 parts of methyl cellosolve and 90 partsof methyl ethyl ketone. In addition, 280 parts of an aluminum hydroxidepowder (manufactured by Sumitomo Chemical Co., Ltd.) were added as aninorganic filler into a resultant mixture to prepare an epoxy resincomposition (epoxy resin varnish). By use of the resin varnish, epoxyresin prepregs and a laminate were produced and evaluated, as in thecase of Example 1. Results are shown in Table 1. TABLE 1 ExamplesComparative Examples 1 2 3 4 5 6 1 2 3 Flame Retardancy [UL94] V-0 V-0V-0 V-0 V-0 V-0 V-2 V-0 V-0 Tracking Resistance (V) 600 600 600 600 600600 600 200 500 Peel Strength (kN/m) 1.57 1.57 1.57 1.57 1.57 1.57 1.571.47 1.47 Heat resistance  5 min ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 10 min ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚⊚ ⊚ 15 min ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ◯ ⊚ 20 min ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Δ ◯ MoistureResistance ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Δ ◯

INDUSTIAL APPLICABILITY

As described above, according to the flame retardant epoxy resincomposition of the present invention, since the phosphorusatom-containing flame retardant polyester resin (C) is used as thehalogen-free flame retardant, it is possible to reduce the amount ofpoisonous gas generated when ignited. In addition, there is an advantagethat a molded article obtained by molding this resin composition isexcellent in flame retardancy, solder resistance, moisture resistance,and tracking resistance. The flame retardant epoxy resin composition ofthe present invention is particularly preferable to prepare prepregs,laminates and printed wiring boards.

1. A flame retardant epoxy resin composition comprising an epoxy resin(A), curing agent (B) and a phosphorus atom-containing flame retardantpolyester resin (C), wherein said phosphorus atom-containing flameretardant polyester resin (C) is obtained by a condensation reaction ora polycondensation reaction of a reactive phosphorus-containing compound(s) represented by the following structural formula (I).


2. The flame retardant epoxy resin composition as set forth in claim 1,wherein a part or all of said curing agent (B) contains a novolac resin.3. The flame retardant epoxy resin composition as set forth in claim 1,wherein an epoxy equivalent of said epoxy resin (A) is in a range of 100to 10000 g/ eq.
 4. The flame retardant epoxy resin composition as setforth in claim 1, wherein said epoxy resin (A) consists of an epoxyresin having no halogen atom in its molecular structure.
 5. A prepregobtained by impregnating the flame retardant epoxy resin composition asset forth in claim 1 into a substrate.
 6. A laminate obtained by moldingthe prepreg as set forth in claim
 5. 7. The laminate as set forth inclaim 6 further comprising a metal foil formed on at least one surfaceof the laminate by laminate molding.
 8. A printed wiring board obtainedby forming a conductive wiring on at least one surface of the laminateas set forth in claim 6.